A turbine impeller (turbine rotor) having a plurality of turbine blades arranged around a main shaft has been known heretofore (for example, see Patent Literature 1). The turbine blades of this turbine impeller are such that, among the blade angles of their fluid outlet trailing edge, a blade angle (angle of a camber surface with respect to the main shaft) βMEAN of a mean section between a hub section (hub side) and a tip section (shroud side) is set based on a predetermined calculation formula with the blade angle βTIP of the tip section, the distance RMEAN from the hub section to the mean section, and the distance RTIP from the hub section to the tip section as variables. This can make the turbine blades capable of improving the performance of a radial turbine.